The laminar burning velocities (LBVs) of ethanol/RP-3 aviation kerosene and aqueous ethanol/RP-3 aviation kerosene premixed flames under the initial pressure of 0.1 MPa, initial temperature of 450 K and equivalence ratios of 0.8−1.4 were obtained by using a constant volume combustion experimental device, and the effects of ethanol blending ratio, volume fraction of water in ethanol and equivalence ratio on the LBV of the mixed fuel were analyzed. Results showed that the LBV of ethanol/RP-3 mixed fuel increased with the increase of ethanol blending ratio; when the ethanol blending ratio in RP-3 fuel was constant, the LBV of aqueous ethanol/RP-3 mixed fuel decreased with the increase of volume fraction of water in ethanol. From analysis of the combustion reaction kinetics, the LBV of the mixed fuel was affected by the combined effects of kinetics and thermodynamics. The experimental data obtained can provide a theoretical basis and technical support for the application of bio-ethanol fuel in aeroengine.

To study the effects of swirler airflow split on the combustor emission characteristics, experimental investigations were conducted on the full annular combustor of dual-axial swirler with airflow ratio of 0.85 and 1.1, respectively, under the ground idle, flight idle and take off conditions. The experimental results indicated that when the airflow ratio increased from 0.85 to 1.1, NOx of flight idle and take off conditions was reduced by 33%−52% and 14%−38%, respectively, while CO and unburned hydrocarbon (UHC) of ground idle were reduced by 23%−49% and 32%−36%. NOx of ground idle for the two cases of swirlers had little difference, and the emission values were both low. CO and UHC emissions were mainly concentrated in the condition of ground idle, and the emission of CO and UHC gradually decreased with the increase of the state, and there was little difference in the emissions of CO and UHC between the two schemes. Within the test range, the CO emission index of the full annular combustor presented a power function decline with the increase of NOx emission index, and a logarithmic increase with the increase of UHC emission index.

Based on the numerical results, the second-order response surface models with high prediction accuracy for the wall average Nusselt number, friction coefficient and comprehensive thermal coefficient of X-type truss channel were built. The influence laws of truss rod diameter ratio, truss rod included angle and truss rod inclination angle on the cooling performance of X-type truss array channel were analyzed, and the optimal parameters were obtained by optimization. The results showed that increasing truss rod diameter ratio and truss rod’s included angle both can greatly improve average Nusselt number, but also increased the friction coefficient accordingly. Enlarging truss rod’s inclination angle first increased and then decreased the average Nusselt number and friction coefficient. Increasing truss rod diameter ratio, truss rod’s included angle and truss rod’s inclination angle made the comprehensive thermal coefficient first increase and then decrease. When truss rod diameter ratio was 0.0750, truss rod’s included angle was 60° and truss rod’s inclination angle was 33.79°, the heat transfer performance of the channel reached the best. When truss rod diameter ratio was 0.067, truss rod’s included angle was 37.88° and truss rod’s inclination angle was 31.36°, the comprehensive thermal performance of the channel was the best.

Opposed-piston 2-stroke (OP2S) compress ignition engines have different fuel-air interactions compared with ordinary CI engines, while air utilization has proved inadequate in measuring fuel-air mixing in CI engines. In this study, the concept of coefficient of richness was proposed as an index of fuel-air mixing in OP2S engines to replace air utilization. Numerical simulation was carried out with CONVERGE software to study the effect of swirl ratio and injector yaw on combustion efficiency in OP2S-CI. Results showed that the coefficient of richness was effective in representing fuel-air mixing regardless of average equivalence ratio. Larger swirl ratio could improve fuel-air mixing during injection while affecting radial distribution of fuel at end of injection. Fuel concentration near either cylinder axis or cylinder wall could hinder fuel-air mixing after injection, decreasing combustion efficiency. Combustion efficiency could vary between the range 0.6 and 1.0 of swirl ratio. Injector yaw may also impact radial distribution of fuel and in turn the combustion efficiency. This effect was taken into account jointly with that from swirl.

To find the optimized cooling structure of turbine blade leading edge, the swirl cooling structure with slot nozzle was established and numerical simulations with the standard k-ε turbulence model were adopted to survey the influence of slot nozzle on the flow and heat transfer characteristics of swirl cooling. Within the studied range of Reynolds number, the non-uniformity of heat transfer for the slot nozzle swirl cooling was 67.8%−71.9% lower than that of the disperse jet swirl cooling along the axial direction. Within the range of the nozzle, the heat transfer intensity of the slot nozzle swirl cooling showed an upward trend along the flow direction. The heat transfer of the bottom surface could be effectively influenced by the inclination angle of the cross-section trapezoid of slot nozzle. When the inclination angle of the cross-section trapezoid was 0.24 rad, the heat transfer intensity was uniformly distributed, and showed a downward trend when the inclination angle of the cross-section trapezoid exceeded 0.24 rad. Once the angle was larger than 0.24 rad, the heat transfer intensity decreased. The slot nozzle height had important effect on the uniformity of heat transfer of swirl cooling and the comprehensive performance was obtained when the height was 3.41 times of the diameter. In addition, the influence of width of the slot nozzle on the swirl cooling was explored.

A deep neural network method based on multimodal fusion was adopted to solve the problem that most current neural network ice prediction methods can only target specific airfoils and do not have the universality of multi-airfoil features. This method used the airfoil cross-section image and the icing condition parameters as inputs, and the two-dimensional ice curve Fourier series fitting parameters as outputs. This deep neural network prediction model realized the prediction ability of the ice characteristics of any symmetric airfoil. The results showed that the proposed model can accurately predict the ice shape under the geometric characteristics of any symmetrical airfoil. The prediction error of the main parameters of the ice shape, such as the ice area and the maximum ice thickness, was kept below 10%.

Targeting the new honeycomb sandwich structure with holes on the sidewall, the coupled heat transfer model of high temperature radiation-heat conduction of honeycomb unit was established. The internal heat transfer mechanism was analyzed by using the finite element method, and the high temperature equivalent thermal conductivity was obtained. The effects of structural parameters, such as hole shape, hole parameters and hole arrangement on equivalent thermal conductivity were discussed, and the calculation correlation of equivalent thermal conductivity was obtained by fitting. Studies showed that the hole shape had little effect on the equivalent thermal conductivity of honeycomb cells. The equivalent thermal conductivity decreased with the increase of porosity, which was less affected by the number of holes. The equivalent thermal conductivity of parallel holes was lower than that of series holes. When the porosity was 14% and the number of holes was 4, the equivalent thermal conductivity was 8.4% smaller than that of series holes, 16.1% lower than that without holes.

A quantitative calculation method of gas leakage in casing flange considering the rough surface morphology and various distributed loads was proposed by using the parallel plate flow theory, which combined the flow factor method and the relationship between contact pressure and contact gap on the rough surface. The influence of internal gas pressure and axial force on gas leakage in casing flange was studied by finite element method. The results showed that with the increase of internal gas pressure, the leakage increased, and with the increase of axial force, the leakage decreased slightly. Finally, the calculated results were compared with the experimental results of leakage, and the maximum errors of leakage under the action of internal gas pressure and axial force were 3.5% and 3.6%, respectively, which proved the effectiveness of the proposed calculation method.

The high-precision numerical simulation technology was used to calculate and analyze the evolution law of the shock wave in the launcher before the cover opening, the load distribution of the front cover at different opening times of the rear cover and the bearing deformation of the front cover under different loading modes. The results showed that the shock wave moved axially in the launcher at a speed of about 450 m/s, and the pressure in the center area of the prism cover was greater than that in the inclined area. The longer opening time of the rear cover from the ignition time indicated the greater peak pressure of the gas reaching the front cover. Considering the safety and opening reliability, the performance was optimal when opening the cover at 0.95 ms. Through the research on the gas load distribution of the prismatic fragile front cover, the regional deformation prediction should be carried out according to the platform area and the inclined area. Compared with the average load loading, it is more conducive to the design of the weak parts of the cover.

For the problem of dynamic response and fatigue failure of titanium alloy acoustic liner under high temperature vibration environment, the vibration characteristics of titanium alloy acoustic liner under high temperature environment were studied by combing simulation analysis and test. The results showed that the calculation results of first-order natural frequency of titanium alloy acoustic liner at 200 ℃ were in good agreement with the test values, and the error was within 8%. Under 40g vibration environment, by comparing the simulation results with the test results, it was found that the error of the velocity response was within 26%, verifying the reliability of the numerical simulation. Using this numerical method, the stress distribution of the acoustic liner under the thermal vibration environment was calculated, and it was found that the maximum stress of the acoustic liner appeared on the honeycomb core, while the overall stress level of the panel was relatively low. With the increase of the height and thickness of the honeycomb core, the stress level of the acoustic liner decreased, while the stress level of the acoustic liner increased with the increasing thickness of the panel, and the influence of the size of the aperture on the strength of the acoustic liner can be ignored.

The three-dimensional numerical model of fully-partitioned pocket damper seal （FPDS）was estab-lished by computational fluid dynamics method. The effects of high inlet pressure, rotational speed and preswirl ratio on the dynamic characteristics of FPDS were studied based on multiple-frequencies elliptic whirling orbits. Results showed that keeping the inlet pressure 7 MPa, the effective damping increased and the crossover frequency decreased with the increasing pressure ratio. For pressure ratio 7, the effective damping increased sharply with the increasing inlet pressure. For inlet pressure 7 MPa, the effective damping was about 10.26 times that of inlet pressure 0.69 MPa, and the system stability was enhanced. Compared with the rotor rotational speed 5 000 r/min, the crossover frequency increased by about 62.2 Hz for rotor rotational speed 25 000 r/min, the effective damping decreased by about 28.5%, and the cross-coupled stiffness increased by about 6.94 times. However, the increase of rotational speed caused vortex in the cavity, which was conducive to reducing the leakage flowrate. The system stability performed best for the preswirl ratio 0. When preswirl ratio increased to 0.8, the cross-coupled stiffness increased by about 4.84 times, and the crossover frequency increased by 24.9 Hz. The effective damping decreased, resulting in the decrease of system stability.

Theoretical and experimental researches on embedded particle damper (EPD) damping method were carried out for vibration control of the cantilever beam structure. The finite element method was applied to analyze the vibration characteristics of the cantilever beam, and the vibration control experiments were carried out under the first, second and third order modal frequencies of the beam. By changing the parameters of the filled particles (particle size, filling rate) and the excitation force, the amplitudes of the cantilever beam under different filling conditions were compared, and the damping ratio was calculated using the half-power method. The discrete element method was used to analyze the rheological behavior of the particles in different cases to determine the optimal design parameters of the dampers. The results showed that: the best damping effect of EPD was achieved when the particle filling ratio was 90%; the particle size of the filled particles was related to the excitation of the system. In this model, when the excitation amplitude was 80 μm, the best effect was achieved when the beam was filled with 8, 6, 1 mm particles at these three modal frequencies, and the damping ratios were 47.5%, 48.7% and 71.2%, respectively, and the damping ratios increased by 1.7, 3.1 and 2.1 times, respectively.

In order to reveal the influence mechanism of tip winglet on the aerodynamic performance of the transonic compressor stage, the aerodynamic characteristics and stability expansion mechanism of compressor stage rotors with different width pressure-side/suction-side tip winglets were studied by numerical method. At the same time, a more systematic structural design method of tip winglet was proposed to optimize the application of tip winglet technology in compressor and improve its stable operating margin on the premise that the pressure ratio and adiabatic efficiency of the compressor stage are kept basically unchanged. The results showed that with the increase of pressure-side tip winglet width, the stable operating margin of the compressor stage increased by 6.01%, 9.90%, 10.76% and 11.43%, respectively. The tip winglet changed the rotor tip flow angle, inhibited the generation of the leakage and the break of the leakage vortex at the tip of rotor blades, improved the flow capacity of the passage, and reduced the separation loss of suction-side stator blades.

To obtain the influence mechanism of non-axisymmetric endwall contouring (NAEC) on the aerodynamic characteristic of a compressor intermediate duct (CID) with large radius change to length ratio under inlet distortion, on the basis of investigating the flow characteristic under inlet distortion, the effects of hub NAEC on the internal flow structure and throttling characteristic of the CID were further explored with numerical method. The results showed that the high total pressure loss and the outlet flow distortion of the CID under inlet distortion were mainly caused by the combined action of the swirl generated by the hub boundary layer separation and the strut corner separation. The proposed NAEC method based on trigonometric function can effectively eliminate the spiral separation nodes on the hub and the strut corner separation, which improved the CID performance significantly, and the total pressure loss coefficient decreased by about 11.4%. In addition, the influence of NAEC on the throttling characteristic of the CID under inlet distortion was different from that of clear inlet condition.

An aerodynamic design method of contra-rotating open rotor (CROR) based on lifting line theory was proposed. Utilizing Lagrange multiplier method, the aerodynamic design control equation of CROR was constructed to find the CROR meeting the thrust demand. Due to the influence of high flight Mach number on the flow characteristics, a positive shock wave was used to simulate the pressure rising process of rotor according to the actuator disk model. Based on the predicted velocity field, preliminary design of CROR was completed utilizing three-dimensional modeling method of compressor. After the preliminary design, turning angle was corrected to meet the thrust demand. The results showed that only two computational fluid dynamics (CFD) calculations and redesign in the whole design process were required to meet the thrust demand. The required turning angle correction was −0.486°. The relative error between design result and thrust demand was −0.32%. The design method was efficient and had good design accuracy.

Numerical simulation method was used to study the stability enhancement effect under different rotational speed matching schemes and the change of first stall stage of counter-rotating compressor (CRC) by performing circumferential groove casing treatment on front and rear rotors of the counter-rotating compressor respectively. The results showed that when the rotational speed of front rotor R1 was higher than that of rear rotor R2, its first stall stage was R1, and when the rotational speed of R2 was equal to or higher than R1, its first stall stage was R2. Casing treatment on first stall stage of the counter-rotating compressor can effectively improve the flow field near blade tip of the treated rotor, including reduction of relative flow angle of inflow, decrease of reverse axial momentum of tip leakage flow, backward movement of interface between tip leakage flow and main flow, and reduction of blade tip blockage, etc., and then improve its stall margin. Generally, the casing treatment can only have a great influence on the flow field of treated rotor, but in special cases, the flow field of non-treated rotor can also be significantly changed.

A robust adaptive attitude controller based on dual-loop design method was proposed for controlling rigid-body attitude in the presence of time-varying rotational inertia, bounded angular velocity and control torque. To satisfy the constraint of angular velocity, the bounded virtual angular velocity was designed to ensure the kinematical equation converge rapidly, and based on barrier Lyapunov function, a variable gain adaptive attitude controller was designed to guarantee the bounded errors between real and virtual angular velocities, in which, recursive adaptive algorithm was constructed to estimate the time-varying rotational inertia and its differentiation. The results showed that the control strategy can make the attitude of the non-cooperative target spacecraft converge exponentially to the desired trajectory, and the convergence trajectory was not affected by external interference and strong interference at the moment of capture. In the entire control process, the angular velocity of the spacecraft was less than 0.4 rad/s and the control torque was less than 10 N·m, thus meeting the physical limitations of the spacecraft.

The model of a control valve of a staged combustion liquid rocket engine was rebuilt in AMESim software environment. And the model of electromechanical actuation system was built in Simulink. Co-Simulation on process of variable thrust, including control valve, actuation system and modified engine model, was conducted. Then perturbance of pressure was introduced during simulation. The results showed that the model of electromechanical actuation system and control valve can reflect the internal parameter changes of each component in the process of variable thrust. The co-simulation maintained the steady-state accuracy of the original engine model, the errors of the main parameters were within the order of 1‰. The self-feedback structure of piston of control valve can restrain the influence of low frequency pressure fluctuation in the conveying pipeline on the thrust of the engine.

In order to find a manufacturing process method for improving the resolution consistency of batch electro-hydraulic servo valves, a radial clamping force distribution model was established to describe the uncertainty of clamping force under parameter perturbation within the radial dimension tolerance range. And the distribution characteristics of the radial clamping force of spool valve couples were obtained. Furthermore, a response surface surrogate model of the mapping relationship between process parameters and radial clamping force distribution characteristic parameters was established. On this basis, global sensitivity analysis of radial clamping force distribution characteristic parameters to process parameters was carried out. The results showed that with the perturbation of radial dimension parameter, the radial clamping force was subject to Weibull distribution. Compared with the radial clearance, spool’s cylindricity had less effect for radial clamping force. Compared with reducing the variation range of the radial clearance, reducing lower limit of radial clearance was more effective to improve the consistency of radial clamping force. Compared with reducing the lower limit of radial clearance, reducing the variation range of radial clearance was more significant to reduce radial clamping force as a whole.

In view of the problems of low fault diagnosis accuracy of aircraft landing gear hydraulic system and difficulty in extracting deep fault features, a fault diagnosis model of landing gear hydraulic system based on the combination of two-stream feature fusion convolutional neural network (TSFFCNN) and particle swarm optimization support vector machine (PSO-SVM) was proposed. The diagnosis model took the pressure signal of multiple nodes as input, the 1D convolutional neural network (1DCNN) and 2D convolutional neural network (2DCNN) parallel multi-channel network structures were adopted to adaptively extract deep feature information, and the deep feature information was fused in the fusion layer. The fusion features were classified into faults through the optimized SVM classifier. In order to verify the proposed fault diagnosis model, a typical aircraft landing gear hydraulic system simulation model was built based on AMESim, and several typical fault type data sets were constructed. The diagnostic results based on the simulation data showed that the accuracy of the proposed fault diagnosis algorithm can reach 99.37%, which can effectively realize the fault diagnosis of the landing gear hydraulic system; compared with other intelligent algorithms, the fault diagnosis model based on TSFFCNN-PSO-SVM had better stability and reliability, higher diagnosis accuracy.

The distortion and stability level of a 2-D ramp and a bump supersonic inlet during a level deceleration flight from Mach number 1.5 with the throttle lever pulled in rapidly to Mach number 1.05 were investigated through flight test. Comparison showed that during the deceleration flight, both total pressure distortion and stability margin of the 2-D inlet declined with the decrease of the engine's conversion speed and then kept stable, while distortion of the bump inlet rose first and then declined and then kept stable, and the stability margin first decreased and then increased slightly and then kept stable. In the first half of the deceleration process, distortion of the bump inlet was higher and stability margin of the 2-D inlet decreased more rapidly, but in the second half of the process, distortion of the two types of inlet was close and stability margin was low. Also the analysis revealed that the inlet stability margin calculated only with flow coefficient actually reflected more information about the flow capacity of the inlet other than that calculated with total pressure recovery coefficient and flow coefficient, so the former was recommended to be used as the evaluation index of inlet stability margin.

Taking the GA(W)-1 airfoil as the research object, the influence law and physical mechanism of the Reynolds number on the aerodynamic characteristics of the airfoil through numerical simulation were investigated. The results showed that the airfoil had strong nonlinear aerodynamic characteristics such as catastrophe and hysteresis under low Reynolds number conditions, and the size of the hysteresis loop gradually decreased and even disappeared with the increase of Reynolds number. The breakup of the separation bubble at the leading edge of the airfoil and the irreversibility of this process constituted the physical origins of the nonlinear aerodynamic characteristics. The nonlinear aerodynamic characteristics of the airfoil under different Reynolds numbers were in accordance with the topological features of the cusp catastrophic model. Therefore, based on the principle of topology invariance, a high-precision topology mapping method was developed to establish the mapping relationship between cusp catastrophic model and nonlinear characteristics of the airfoil, then the nonlinear aerodynamic characteristics of the airfoil at low Reynolds number were successfully predicted by the equilibrium surface of the cusp catastrophic model, and the model error was less than 5%.

In order to study the performance and stability of turbofan engine under mass injection and pre-compressor cooling (MIPCC), the steady-state performance of turbofan engine was numerically simulated by considering three factors: inlet mixing heat exchange, modification of thermophysical properties of working fluid and modification of component characteristics. The calculation results showed that the thrust of engine under MIPCC greatly increased due to the increase of intake flow, in which the inlet mixing heat exchange is the direct factor contributing to the increase of intake flow, while the changes of thermophysical properties of working fluid and component characteristics lead to the decrease of the thrust of engine. Even if with high water-air ratio, the thrust level can still be greatly enhanced by intake flow. Inlet mixing heat exchange can make fan work closer to the surge point, however, with the increase of water-air ratio, the stability of fan and high-pressure compressor both rose.

To effectively detect the defects of pits, scratches and abrasions on the raceway surface of Si₃N₄ ceramic bearing inner ring in aviation power system, median filter was used to remove original image scattered noise of Si₃N₄ ceramic bearing inner ring channel, and conduct its processing image's shear wave transform, and the normalized threshold surface method was adopted to reconstruct the conversion coefficient of shear wave, enable shear wave inverse transformation for defect enhancing image, gray threshold segmentation for defect enhancing image classification and recognition, and position to extract the defect. The surface defect detection method of Si₃N₄ ceramic bearing inner racetrack based on shear wave transform can effectively detect the surface defect of Si₃N₄ ceramic bearing inner racetrack. This method can extract surface defects of inner raceways of Si₃N₄ ceramic bearing with 97.50% accuracy, which can meet the expected requirements.

Considering the problem of low fault identification accuracy caused by insufficient sample size and complex working conditions, a fault diagnosis method of rolling bearing with small sample based on Markov transition field and multidimensional supervised module convolutional neural network (MTF-MSMCNN) was proposed. The one-dimensional rolling bearing signal was transformed into two-dimensional feature image using MTF coding method to preserve temporal correlation. Multidimensional supervision module (MSM) was presented to monitor important fault features in both spatial and channel dimension and assign weight adaptively, which can improve the model’s ability to capture key features. MSM was embedded into the convolutional neural network to build a MSMCNN model. The complex working conditions were constructed through experiments, and the MTF images were input into the MTF-MSMCNN network model for fault diagnosis. Two data sets were used to verify the model validity. The experimental results showed that the MTF-MSMCNN had only 10 samples in each type of fault training set, and its fault diagnosis accuracy can still reach about 90% under 0 dB noise pollution. Compared with other diagnostic models, the method proposed had higher recognition accuracy, stronger generalization ability and anti-noise performance under the conditions of small samples, variable working conditions and noise interference.

Charge design methods affect the ballistic performance of the engine. In order to improve the charge utilization rate, UG NX and MATLAB software were used for modeling and programming of the calculation, and the function relationship diagram of the combustion surface, the residual drug rate and the design parameters during the combustion process of the drug column was obtained, and finally the example analysis was carried out. The results showed that when D was defined as the outer diameter of grain, and the relative radius of circular groove $ r $ was (0, 0.05D), the relative radius of the hole in the cylindrical section $ {R_2} $ was (0.1D, 0.4D), the relative radius of the circular center of the circular groove $ {R_3} $ was ($ {R_2} $, 0.42D) and the length of the cylinder $ {L_2} $ was (0.4D, 1.53D), the combustion law was progressive at first and then regressive. The waste grain rate and the change trend of $ r $ and $ {R_2} $ monotonically decreased, the waste grain rate and the change trend of $ {L_2} $ monotonically increased, and the waste grain rate and the change trend of $ {R_3} $ first increased and then decreased. From the aspects of weight reduction, improvement of the strength, processing and manufacturing, it is recommended to give priority to the dished head. The maximum relative error between the calculated result and the actual data was 0.078%.